Channeling of incident ions and radiation-enhanced diffusion of the ion-created defects have been shown to be major components of the ion damage profile. Our earlier results showed a deeper damage profile in InP, compared to GaAs, when subjected to the same ion bombardment conditions. Computer simulations demonstrated that this can partially be attributed to the greater ion channeling range in InP. In this article the role of defect diffusion in InP, through experiments coupled with simulations, is delineated. The multiple quantum well (MQW) probe technique is used to determine the amount of damage by measuring the change in low temperature photoluminescence of quantum wells before and after argon ion bombardment. A blocking superlattice is added to the MQW heterostructure and is proven effective in preventing damage from propagating into the material below it. By correlating the experimental results with computer modeling, an estimate of the defect diffusion constant is obtained and it is found to be in the range of 4×10−15–1×10−14 cm2/s. These high values for diffusion are justified with experimental results that illustrate the presence of radiation-enhanced diffusion mechanisms during ion bombardment.